A cigarette contains about 10 milligrams of nicotine. About 1 to 2 milligrams get into the blood stream and hit the brain's reward center within 10 seconds after inhalation.
An average smoker takes 10 puffs per cigarette over a five-minute period. For a person who smokes 1 1/2 packs daily, his brain gets 300 hits of nicotine.
That nicotine plugs into receptor ports on brain cells stimulating the production of dopamine. Dopamine then turns the brain's pleasure center on.
At the same time, nicotine molecules plug into another set of inhibitory neurons, jamming their ability to turn off the pleasure center. The subsequent high lasts about an hour, the time it takes for nicotine in the blood to subside to the point where the inhibitory system can be reactivated.
"There's no other outcome than excitation when you've got nicotine in the system," he added. "It would be hard to design a drug that acts on the reward center that would be more effective than nicotine."